The new Sherlock from the BBC show frequently mentions his 'memory palace". In case any of you were wondering what he was talking about, I'll tell you: the memory palace (or theatre as I more usually here it called) (wikipedia calls it palace but also gives it the more formal and latinate name of memory loci) is an old memory trick, invented or at least used by the ancient Greeks and perfected in the Middle Ages. It remains to this day the best memory aid there is. The best explanation I have seen of how exactly it works comes from an episode of James Burke's The Day The Universe Changed (incidentally, one of my favourite television shows ever.)
The explanation of memory theatre begins at the 8:07 mark, but by all means, watch the whole thing.
Memory theatre is important to us Catholics as much of our art and symbolism and even our architecture arise from this mental trick being given a physical form in our churches and cathedrals. I explain how this is done on a small scale in this old post here on my old church. It is good to learn about these things, and to better understand from whence we come.